Vehicle steering system utilizing desired-value-dependent control segment

Abstract

A vehicle steering system has a desired-value generator arrangement which is actuated by a manual steering device. The desired-value generator arrangement is connected with a hydraulic actuating unit for the steered vehicle wheels by a regulating system. A modified PD control, along with taking a control segment into account, provides a precise operation of the actuating unit analogously to the operation of the manual steering device.

What is claimed is: 
     
       1. A vehicle steering system, comprising: a manual steering device, configured to be operated by a vehicle driver,   steered vehicle wheels operatively connected with the steering device,   a desired-value generator actuatably connected with the steering device, and   a hydraulic actuating drive operationally connected with the vehicle and configured to be controlled by an electrically actuated valve configured such that an electric valve current thereof is dependent on a regulating segment determined by a desired-value actual-value comparison of the steering angle or a quantity correlated therewith, and the electric valve current is controlled as a function of a desired-value-dependent control segment,   wherein the control segment is proportional to a chance rate of a desired value.   
     
     
       2. The vehicle steering system according to claim 1, wherein the regulating segment comprises a proportional segment and, above a threshold value of a regulating difference, a differential segment of the regulating difference. 
     
     
       3. The vehicle steering system according to claim 2, wherein the control segment is proportional to a change rate of a desired value. 
     
     
       4. The vehicle steering system according to claim 1, wherein the electric valve current is proportional to an actuating speed of the hydraulic actuating drive. 
     
     
       5. The vehicle steering system according to claim 4, wherein the control segment is proportional to a change rate of a desired value. 
     
     
       6. The vehicle steering system according to claim 5, wherein the regulating segment comprises a proportional segment and, above a threshold value of a regulating difference, a differential segment of the regulating difference. 
     
     
       7. The vehicle steering system according to claim 1, wherein the desired-value generator is configured to operate as a function of driving speed such that, according to a product, the desired value is a function of a position of the manual steering device and the driving speed. 
     
     
       8. The vehicle steering system according to claim 7, wherein the control segment is proportional to a change rate of a desired value. 
     
     
       9. The vehicle steering system according to claim 8, wherein the regulating segment comprises a proportional segment and, above a threshold value of a regulating difference, a differential segment of the regulating difference. 
     
     
       10. The vehicle steering system according to claim 9, wherein the electric valve current is proportional to an actuating speed of the hydraulic actuating drive. 
     
     
       11. The vehicle steering system according to claim 1, wherein the desired-value generator comprises a unit configured to compensate for non-linearity between an actuating path of the hydraulic actuating unit and a steering angle of the steered vehicle wheels. 
     
     
       12. The vehicle steering system according to claim 11, wherein the control segment is proportional to a change rate of a desired value. 
     
     
       13. The vehicle steering system according to claim 12, wherein the regulating segment comprises a proportional segment and, above a threshold value of a regulating difference, a differential segment of the regulating difference. 
     
     
       14. The vehicle steering system according to claim 13, wherein the electric valve current is proportional to an actuating speed of the hydraulic actuating drive. 
     
     
       15. The vehicle steering system according to claim 14, wherein the desired-value generator is configured to operate as a function of driving speed such that, according to a product, the desired value is a function of a position of the manual steering device and the driving speed. 
     
     
       16. The vehicle steering system according to claim 1, wherein the desired-value generator is configured to be provided with an input for an autonomous control as a function of given parameters. 
     
     
       17. The vehicle steering system according to claim 16, wherein the control segment is proportional to a change rate of a desired value. 
     
     
       18. The vehicle steering system according to claim 17, wherein the regulating segment comprises a proportional segment and, above a threshold value of a regulating difference, a differential segment of the regulating difference. 
     
     
       19. A vehicle steering method, comprising the steps of: manually operating a steering device, connected to a desired-value generator controlling a hydraulic actuating drive operationally connected with the vehicle wheels via an electrically actuated valve with an electric valve current thereof dependent on a regulating segment determined by a desired-value actual-value comparison of steering angle or a quantity correlated therewith, and   controlling the electric valve current as a function of a desired-value-dependent control segment to steer the vehicle wheels with a rough adjustment having no delay and precision adjustment taking place by way of the regulating segment,   wherein the control segment is proportional to a chance rate of a desired value.